1. Field of the Invention
The present invention relates to a dielectric resonator such as a dielectric filter for use in the microwave band or millimeter wave band, an oscillator, a sharing device, and a communication device each including the dielectric resonator.
2. Description of the Related Art
In order to realize advanced mobile communication services and multi-media communication services, it is necessary to transmit a large quantity of information at an ultra high speed. For this purpose, the millimeter wave band having a wide band width is suitable. As new uses utilizing effectively the characteristics of the millimeter wave band, in addition to the uses of communication, a motorcar radar for preventing collisions is an example. It is much expected that the millimeter wave radar serves the assurance of safety required particularly when it mists or snows, for which a conventional laser radar utilizing light is ineffective.
If a conventional circuit configuration formed mainly of microstrip lines is used in the millimeter wave band, Q is reduced with the loss increased. Further, as regards a TE.sub.01.delta. dielectric resonator, used widely conventionally, a great amount of resonant energy is leaked to the outside of the resonator. For this reason, in the case of the resonator and the circuit used in the millimeter wave band and having a small relative size, there is the problem that lines are undesirably coupled to each other, and the design and the reproducibility of the characteristics become difficult.
To solve this problem, the inventors have devised PDIC.TM. (Planar Dielectric Integrated Circuit), and proposed a millimeter wave band module using this technique.
An example of the planar circuit type dielectric resonator incorporated in the module is disclosed in Japanese Unexamined Patent Publication No. 8-265015.
FIG. 19 shows the configuration of the dielectric resonator device. In FIG. 19, there is shown a dielectric plate 3, and on the opposite main faces of the dielectric plate 3, electrodes are formed with electrode-non-formation sections which are circular, have a predetermined size, and are opposite to each other, and the upper electrode of the dielectric plate 3 is shown at a numeral 1 and the electrode non-formation sections at numerals 4a and 4b. With this configuration, the section of the dielectric resonator device, sandwiched between the electrode-non-formation sections, is used as the dielectric resonator section.
In a device employing the planar circuit dielectric resonator as shown in FIG. 19, metallic adjusting screws are provided for a shield case 24 in such a manner that the insertion amount of the screws in the shield case can be adjusted. With the adjusting screws, the resonant frequency of the dielectric resonator sections and the coupling factor between the adjacent dielectric resonator sections can be adjusted.
However, in the case of the metallic adjusting screws used, an insertion loss is produced in the adjusting screws with the unloaded Q reduced, when the adjusting screws are near to the resonator sections. For this reason, there is the problem that when the dielectric resonator device is used as a filter, its filter characteristics are deteriorated. Further, there is caused the problem that the outside size of the device is large since the adjusting screws are partially projected to be on the outside of the shield case.